EA have revealed that they have delayed the Xbox 360 edition of the Medal of Honor multiplayer beta. On the official Medal of Honor-blog they've written that:
"As for the Xbox 360 version of the beta, we are delayed and we apologize. To the Xbox 360 community, we say thank you for your continued patience. We are working to fix the issues that have caused this delay and, like you, we're eager to get the game up and running at quality."
No explanation or mention of what these issues are, or when the beta can be expected, but I guess we will just have to wait and see.